Because this is 4 sided, it is 360°(in total)
The shape is parallel on 2 sides(shown by the red arrows), so (5x)° = 90°
5x = 90
x = 18°
You can add all the angles together and set it equal to 360°
90° + (5x)° + (5(y+11))° + (4y-10)° = 360°
Since you know 5x is 90°, you can plug it in
90° + 90° + (5(y+11))° + (4y-10)° = 360°
180° + (5(y+11))° + (4y-10)° = 360° Subtract 180° on both sides
(5(y+11))° + (4y-10)° = 180°
5y + 55° + 4y - 10° = 180°
9y + 45° = 180°
9y = 135°
y = 15°
x = 18°, y = 15°
